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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Effect of redox conditions in the degradation of (RS)-MCPP during biological treatment of synthetic wastewater in an anaerobic membrane bioreactor (AMBr)

Muhammad Yuzir, Muhamad Ali January 2008 (has links)
The aim of this research is to investigate the effect of mecoprop (RS-MCPP) degradation in an anaerobic membrane bioreactor (AMBr) under a range of redox conditions (methanogenic, nitrate reducing and sulphate reducing). A method was developed for the analysis of (RS)-MCPP in aqueous form using High Performance Liquid Chromatography (HPLC). The study was carried out in five phases. Initially, Phase I investigated the effect of elevated (RS)-MCPP on AMBr under methanogenic conditions. In this phase, increasing concentrations of (RS)-MCPP (5 - 200 mg. L-1) promoted a progressive increases in the (RS)-MCPP substrate utilisation rate (SUR) (0.15 to 3.19 [ig-mgVSS' 1. d"'). However, the COD removal efficiency decreased gradually from 98 % to 94 % as the (RS)-MCPP concentration increased in the feed from 50 - 200 mg. L-1, respectively. Phase II investigated the effect of denitrifying conditions on (RS)-MCPP degradation. Results showed that (RS)-MCPP removal efficiency and (RS)-MCPP SUR improved from 2- 47 % and 0.5 to 60.7 Rg. mgVSS-l. d-1, respectively as the COD/N-NO3-1 ratio and OLR were reduced from 250 to 0.2 and 1.51 to 0.07 kgCOD M, 3 A-1, respectively. Phase III investigated the effect of sulphate-reducing conditions on (RS)-MCPP degradation. Results showed that sulphidogenic conditions were less effective than nitrate reducing conditions with an average (RS)-MCPP removal and (RS)-MCPP SUR at 20(±10.7) % and 16.4 ýtgm. gVSS-lffl, respectively. Phase IV investigated the effect of HRT on the kinetics of (RS)-MCPP degradation. The robustness and stability of AMBr was also investigated in response to hydraulic shock loads on the biomass imposed. Results showed that the AMBr is stable to a large transient hydraulic shock loads, and it recovered rapidly to baseline performance after the hydraulic shock load had ended. High (RS)-MCPP degradation (up to 75 %) and utilisation rates (43 gg. mgVSS'1. d") were observed at long HRT (16.9 days). Phase V was a confirmatory experiment study to investigate the possible effects of trace quantities of oxygen that had been present in the reactor headspace and the effluent tank during Phase IV. This confirmed that the system performance towards (RS)-MCPP biodegradation had not been affected by trace oxygen levels when comparison are made. The molecular-based method, fluorescent in situ hybridisation (FISH) was used for the direct identification and enumeration of microbial communities in the AMBr sludge. In general, FISH results showed populations were dominated by methanogenic archaea in methanogenic phase (Phase I and IV) comprising between 55-66 % of the DAPI count. However, as anoxic condition were introduced in Phase II and III (nitrate reducing and sulphate reducing), the results identified a definite population shift, with the predominance of eubacteria (70-86 % of the DAPI count). The two methanogenic genera detected were Methanosaeta and Methanosamina. Of these two genera, the former was dominant in the reactor accounting for 57-100 % of the total methanogenic archaea. Furthermore, a comparison of (RS)-MCPP utilisation rates in each phase of the research revealed wide ranges (RS)-MCPP degradation efficiency and (RS)-MCPP SUR, however, although changes were observed in the composition of the bacterial population, no direct linkage could be made with any of the individual groups identified by FISH.
2

Aluminium smelting : the toxicity, scale and longevity of fluoride pollution in the environment

Brougham, Kate January 2011 (has links)
The release of fluoride from the production of aluminium, and the subsequent impacts of deposition in the environment, is well documented (Weinstein and Davison, 2004). However, changes are occurring within the industry, driven by technological advances and growth in global manufacture, which have the potential to alter the impact of the aluminium industry on the environment. There needs to be a better understanding of the toxicity of Sodium hexafluoroaluminate (cryolite, Na3AlF6), the impact of modern operating procedures on the release of particulates in to the environment, and finally, an investigation of the longevity of fluoride concentrations in vegetation from industrial pollution once emissions cease (EU, 2008). The toxicity of cryolite exposure to 1st and 3rd instar Diamondback moth larvae (Plutella xylostella (L), Lepidoptera: Plutellidae) was studied through a series of bioassays. There were inter-stage variations in both the lethal and sub-lethal responses to cryolite, whereby low mortality corresponded with high sub-lethal effects and vice versa. A dose-related response threshold was observed in both instars indicating that the physical nature of cryolite plays a role in the toxic mode of action. The comparative toxicity of cryolite from the pot-rooms of Lynemouth smelter and pesticide Kryocide© (Cerexagri, Inc) was investigated along with the role of particle size and the purity of the cryolite particulate in the mode of action. Although both physical and chemical factors played a role in toxicity, these factors formed a hierarchy and the mode of action had a significantly over-riding chemical grounding. Dust samples were collected from the vicinity of Lynemouth smelter for a period of 10 months in order to quantify the impact of modern aluminium production on the environment. Although the volumes of dust collected at any one site were lower than the European Community Short Term Ambient Guideline Concentration of Particulate Matter, dust deposition corresponded with aluminium production rates at the smelter showing that, despite Better Available Technology at the smelter, modern aluminium production still impacts on the environment. When Anglesey Aluminium Metals Ltd ended its operations in September 2009, it created a unique opportunity to assess the long-term impacts of fluoride pollution on the environment. Samples of soil, leaves and lichens were collected to monitor the changes in fluoride content over a 15 month period. The results showed that fluoride contamination of vegetation from industrial processes had a short-term impact once emissions ceased and that mineral-based soils had limited potential as contaminating sources for plant uptake. The mode of action of cryolite toxicity and the impact of waste disposal and fugitive release of cryolite in to the environment are discussed.
3

Organic phosphonate metabolism by marine bacteria

Villarreal-Chiu, J. F. January 2012 (has links)
Phosphonates are a family of organophosphorus compounds characterized by the presence of a carbon- phosphorus bond. This bond provides greater chemical stability compared with analogous compounds containing the more reactive carbon-oxygen-phosphorus linkage (Quinn et al., 2007). Hence, it is important to consider their accumulation in the environment and possible toxic threat to ecosystems. This study explored the distribution ofphosphonate metabolic pathways among sequenced microorganisms and their prevalence and occurrence in the environmental metagenomic database using bioinformatic tools. Experiments carried out on a number of marine representative strains confirmed the capacity of their predicted phosphonate catabolic enzymes to utilize phosphonates for bacterial growth when supplied as phosphorus and to some extent, as nitrogen sources. The bacterium Roseovarius nubinhibens ISM was able to . produce methane through the aerobic degradation of methylphosphonate even in the presence of Pi concentrations up to 7.5mM. Also, this strain exhibited the unique characteristic of producing both polyhydroxybutyrate and polyphosphate concurrently as result of nutritional stress through either phosphorus or nitrogen limitation. Haloquadratum walsbyi was confirmed to be the only known archaeon to possess a phosphonate degradation pathway, and experiments confirmed the capability of this strain to consume phosphonates 2AEP, MPn and glyphosate as phosphorus sources.
4

Arsenic removal from wastewater using dolomitic sorbents

Salameh, Yousef January 2012 (has links)
Dolomite and charred dolomite have been evaluated for use in the removal of dissolved arsenic anions (arsenate and arsenite) from wastewaters. Experimental equilibrium isotherm investigations, kinetic experiments and fixed-bed column experiments have been used to assess the uptake from a wide range of aqueous arsenic solutions, employing both dolomite and thermally processed (charred) dolomite. Scanning electron microscopy, X-ray diffraction, FTIR analysis, Zetasizer (size analysis), mercury porosimetry and inductively coupled plasma atomic emission spectrometry (ICP-AES) have been utilized to aid in the evaluation of the dolomitic materials as adsorbents. Equilibrium experimental data have been analyzed using Langmuir, Freundlich, Henry and Redlich-Peterson isotherm models. Kinetic data have also been analyzed using elementary first and second reaction models and an intra particle diffusion model. The data from the models have been used to help determine the mechanism of arsenic removal. Dolomite and its thermally activated dolomites have shown potential as a cost effective material for use in the removal of arsenic from drinking water. Modifying the surface of the dolomite by charring, helped to overcome obstacles encountered with the adsorption of arsenic onto raw dolomite. The charred dolomite shows significant potential in removing As (III) from aqueous solutions and has been shown to operate effectively under a wide pH range. The thesis provides evidence for ion exchange, adsorption and precipitation mechanisms, to account for the removal of arsenic from aqueous solutions using dolomite and charred dolomite.
5

The removal of fuel oil compounds from groundwater for potable supply

Hall, Samuel Clelland January 2005 (has links)
This study was a joint project between the Environmental Engineering Group of the Department of Civil and Environmental Engineering - University College London and Anglian Water. The project was funded by an EPSRC CASE studentship (award No. 00800074) with Anglian Water. Cases of fuel oil contamination of groundwater are common throughout the world. The leakage of above and below-ground fuel storage tanks pose a significant threat to groundwater and in some cases potable water supply (PWS) boreholes. Although in-situ remediation methods are fundamental to a remediation strategy and can remove large amounts of hydrocarbon contamination, practical steps must sometimes be taken at PWS boreholes down- gradient of the contamination source to protect the supply. This study details the optimisation of a modular post-abstraction remediation system incorporating air-stripping and granular activated carbon (GAC) technologies. Emphasis throughout the experimental phase of the study is placed on methyl-tertiary-butyl-ether (MTBE) and benzene, toluene, ethylbenzene and xylene (BTEX) compounds. MTBE and BTEX compounds represent those most likely to reach the borehole after a contamination event, and also those which pose the greatest risk to human health. Stringent remedial targets were implemented, based upon world-wide drinking water standards. For benzene the remedial target was 1 ig/L and for MTBE the remedial target was 5pg/L. Utilising high performance stainless steel structured packing with air-to-water ratios ranging from 9 - 86, air-stripping removal efficiencies for MTBE ranged from 20 - 89%, whilst removal efficiencies for benzene ranged from 52 - 90%. The results of the study suggested that the removal efficiency of MTBE was dependent upon the air-to-water ratio, whilst the removal efficiency of benzene was independent of the air-to-water ratio. Utilising F400 GAC, the total adsorptive capacity for MTBE was 3.45 mg/g, whilst the adsorptive capacity for benzene was 2.72 mg/g. However, the general results suggested that benzene was adsorbed much more readily than MTBE. Utilising F600 GAC, the total adsorptive capacity for MTBE was 1.45 mg/g, whilst the adsorptive capacity for benzene was 1.96 mg/g.
6

Removal of pollutants from water using Calix (4) Pyrrole derivatives and silica based compounds: Thermodynamic studies and environmental applications

Khalife, Rasha Mohammad January 2008 (has links)
This thesis is concerned with an investigation of the thermodynamic parameters of complexation of calix[4]pyrrole derivatives with anions and metal cations, as well as the use of calix[4]pyrrole oligomers and silica based materials aiming at the removal of polluting ions from aqueous solutions.
7

Temporal and spatial trends of persistent organic pollutants in air and soil : implications for their sources and environmental cycling

Schuster, Jasmin January 2011 (has links)
Persistent organic pollutants (POPs) are defined by their characteristic properties in the environment, such as adverse effects on humans and other organisms, a low degradation rate, a potential for bioaccumulation and long range-transport. These properties are the reason that POPs are monitored in remote regions, like the Polar Regions and open oceans, even though they were mostly used in populated areas (urban or rural). A group of POPs was banned under the Stockholm Convention on Persistent Organic Pollutants in 2001 by a number of countries and more chemicals have been added to the list subsequently. To assess the effect of international regulation more information about the long-term fate of these chemicals, the transport processes and the exchange between different environmental media is needed. The first part of this thesis describes long-term trends of POPs such as polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in the environmental compartment air. One study discusses the trends that were observed with passive air samplers in remote locations along a transect across the UK and Norway. The air• concentrations monitored from 1994 to 2008 at 11 sites showed a general decline. While the total air concentrations decreased with increasing latitude, the decline rates did not differ between sampling sites. A second study discusses the trends of PCBs in the UK atmosphere for urban and rural sites. As in the remote areas, a steady decline was observed following first order kinetics. The PCB concentrations at each sampling site were directly proportional to the population density of the area. It was therefore concluded that air concentrations of PCBs are currently still defined by the direct input from primary source emissions and the observed decline mirrors a decline in emission. In order to assess the fate of POPs in other environmental media soil cores were collected following the transect for the passive air data across the UK and Norway. The soil cores were collected at identical locations ten years earlier. A direct comparison of the data between the sampling years proved that the decline in soil is more variable than in air for most monitored POPs. While there were nearly no changes in soil concentrations of organochlorine pesticides, there was a slight decline for PCBs and a strong decline for PBDEs. Changes in the burden, of PCBs per unit soil organic matter between 1998 and 2008 indicate the approach of soil-air equilibrium for the monitored sites. However chiral data and atmospheric data from the regions indicate that the influence of re-volatilization contributed only a minor component of the air burden of PCBs in remote areas of northern Europe. Important tools in monitoring regional and temporal trends of POPs are passive air samplers, which can be deployed at low cost in remote areas. A new type of sampling medium. the sorbent-impregnated polyurethane foam (SIP) disk, was assessed for its applicability for long-term monitoring of PCBs, PBDEs and hexachlorobenzene. Long-term deployment is a necessity for areas with low concentrations. In order to estimate the most precise atmospheric concentrations from the chemicals sequestered on the sampling medium, it would be preferable if the sampler and atmosphere are not in equilibrium and the sampled air volume is therefore directly proportional to the deployment time. It was found that the SIP disk presents a valid alternative to other established passive air sampling media. The last part of the thesis discusses a group of emerging POPs, the perfluorinated compounds (PFCs). PFCs were monitored in a passive air sampling campaign in different Asian countries. Differences were observed in the PFC composition at different sampling sites. These were explained with different usage pattern and regulations in the different countries. Further research is required to gain deeper understanding the transfer mechanism between different environmental compartments for POPs. The application of a model is needed to assess the increasing influence of secondary sources, i.e. revolatilisation from soils on atmospheric concentrations. While long-term studies for emerging compounds already exist, it is necessary to establish similar monitoring campaigns for emerging chemicals.
8

Modelling the sources, fate and environmental behaviour of persistent organic pollutants

Paul, Alexander George January 2011 (has links)
This thesis attempts to logically follow the full lifecycle of a 'new' persistent organic pollutant (POP), perfluorooctane sulfonate (PFOS). A new estimate of the global historical production for perfluorooctane sulfonyl fluoride (POSF) was produced, before focusing on deriving the first estimate of the global historical environmental releases of PFOS. The total historical worldwide production of POSF was estimated to be 96,000 tonnes between 1970- 2002, with an estimated global release of 45,250 t to air and water between 1970-2012. Estimates indicated POSF-derived products are the major direct source of PFOS emissions, resulting in an estimated release of 450-2700 t into wastew31er streams over the same period. Due to the physiochemical properties of PFOS (soluble in water, negligible vapour pressure, and limited sorption to particles), emissions from consumer products including stain repellent treated fabrics, waterproof apparel, and aqueous fire fighting foams were expected to be largely to waste water. The following papers saw two existing multi-media environmental fate models reparameterised to explore the role of emissions from diffuse consumer use. PFOS emissions were linked to waste water treatment plants, partitioning and emissions uncertainty were explored, and annual fluxes of PFOS were estimated from European rivers at a local and continental scale. A good agreement, generally within a factor of three between modelled emissions derived from population density and measured freshwater PFOS concentrations, was observed. The final paper is a slight departure from the others submitted in this thesis. This paper returns to 'classical' POPs, but looks forward in time to try and understand the potential impact of climate change on POP chemicals. Overall. predicted changes were small even under the most conservative scenarios, resulting in slightly increased volatilisation and degradation in air from a drier and warmer south-western Europe, corresponding to a transfer and redeposition of POPs to the cooler and wetter north-eastern Europe.
9

Investigating the relationship between shear and floc fate using CFD

Bridgeman, Jonathan Matthew January 2006 (has links)
No description available.
10

A study of the physicochemical properties of chlorinated solvents with reference to their transport and fate within sandstone aquifers

Harrold, Gavin January 2004 (has links)
No description available.

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